Abstract
Encosternum delegorguei Spinola (Hemiptera: Tessaratomidae) are consumed as relish and with traditional claims of having medicinal roles in the South-Eastern districts of Zimbabwe. However, very little has been explored scientifically to validate these claims. The current study was conducted to investigate bio-active compound composition and diversity of stable antibacterial activity from E. delegorguei extracts. Methanol, ethanol and aqueous extractions of E. delegorguei were performed followed by qualitative, quantitative analyses of phytochemical/bioactive compounds and determination of antibacterial activities using disc diffusion method on ten clinically important microbes. Alkaloids, flavonoids, anthraquinones, tannins, phlobatannins, steroids, triterpenoids and cyanogen glycosides were detected in the insect extracts. Flavonoids were detected in significantly higher concentrations in unprocessed compared to processed insects. Mean DPPH free radical scavenging activities were 78% and 88% for traditionally processed and raw insect extracts respectively. Traditional processing resulted in reduction of bioactive compounds (22.2% total phenolics; 68.4% flavonoids) and free radical scavenging activities by 10%. However, it resulted in an increase of cyanogen glycosides by 65.7%. Methanol extracts produced highest mean inhibition zones of 20 mm while aqueous and ethanol extracts had mean inhibition of 0 to 15 mm as compared to control with 20-40 mm. High flavonoids levels could be beneficial to consumers. However, a potential trade-off from elevated levels of cyanogen glycosides after processing needs further investigation. The free radical scavenging activity displayed by E. delegorguei extracts indicate a potential source of natural anti-oxidants that can be formulated into commercial products.
Highlights
The Edible Stinkbug, Encosternum delegorguei Spinola (Hemiptera: Tessaratomidae) is distributed widely in subtropical woodland and bush veldt with occurrences in Zimbabwe and northern provinces of South Africa (Dzerefos, Wtkowski, & Toms, 2009; Picker, Griffiths, & Weaving, 2004)
The free radical scavenging activity displayed by E. delegorguei extracts indicate a potential source of natural anti-oxidants that can be formulated into commercial products
Much of the studies done so far were centred on the nutritional compositions of edible insects that included the African palm weevil, Rhychophorus phoenicis (Elemo, 2011), Edible Stinkbug, E. delegorguei (Teffo et al, 2007) and a wide range of other insects (Defoliart, 1995; Banjo, Lawal, & Songonuga, 2006)
Summary
The Edible Stinkbug, Encosternum delegorguei Spinola (Hemiptera: Tessaratomidae) is distributed widely in subtropical woodland and bush veldt with occurrences in Zimbabwe and northern provinces of South Africa (Dzerefos, Wtkowski, & Toms, 2009; Picker, Griffiths, & Weaving, 2004). In Zimbabwe, the Edible Stinkbug is restricted to the southern most parts which include the Nerumedzo region in Bikita (approximately 20°1'23.22"S, 31°41'17.65"E) and Zaka (approximately 20°4'28"S, 30°49'58"E) districts in Masvingo province (Chavhunduka, 1975; Mawere, 2012). Encosternum delegorguei is an important source of income in parts of Zimbabwe and South Africa. Teffo, Toms, and Eloff (2007) reported the nutritional importance of the Edible Stinkbug consumed in Limpopo province, South Africa. The insects were reported to have high protein, fat, amino acid, minerals and vitamin contents
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